Hearing effects of nonoccupational sound exposure evaluated by temporary threshold shift

In the 1960s, the relation between the acoustical characteristics of sound exposure and the sound-induced temporal threshold shift (TTS) of people were carefully investigated by Shoji et al. [J. Acoust Soc. Am. 48 978−987 (1970); 6th ICAA−2−8, pp. A9−A12 (1968)]. Based on these studies, an equation that estimates TTS at various test frequencies was proposed as a function of the TTS−critical−band levels. In this presentation, therelation between the sound exposure and the TTS will be reviewed, and a prototype TTS meter that estimates TTS in real time operation will be introduced. The hearing effects of some nonoccupational sounds at different places (Pachinkoparlor, disco, and livehouse) were evaluated with the TTS levels as the indicator. The sounds from portable musicplayers and music instruments of or chestra were also evaluated. The TTS levels were measured for shorttime sound exposure and compared to long−term estimates using the TTS meter. In some cases, after 2− or 4−h sound exposure, the estimated TTS levels at the test frequency of 4 kHz reached almost 20 dB.